/*  This file is part of libravatarserv.
 *  Copyright © 2022 tastytea <tastytea@tastytea.de>
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, version 3.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "hash.hpp"

#include "types.hpp"

#include <algorithm>
#include <memory>
#include <string>
#include <string_view>

#define CRYPTOPP_ENABLE_NAMESPACE_WEAK 1 // necessary for MD5
#include <cryptopp/cryptlib.h>
#include <cryptopp/filters.h>
#include <cryptopp/hex.h>
#include <cryptopp/md5.h>
#include <cryptopp/sha.h>

namespace libravatarserv::hash {

std::string generate_hash(const algorithm_t algo, const std::string_view text) {
    using namespace CryptoPP;

    SHA256 sha256;
    Weak::MD5 md5;
    HashTransformation *algo_to_use{&sha256}; // HashFilter calls free()?
    if (algo == algorithm_t::MD5) {
        algo_to_use = &md5;
    }

    std::string hash;
    StringSource s(text.data(), true,
                   new HashFilter(*algo_to_use,
                                  new HexEncoder(new StringSink(hash))));
    std::transform(hash.begin(), hash.end(), hash.begin(), ::tolower);

    return hash;
}

std::string find_email(const request_t &req, const fs::path &directory) {
    bool default_present{false};
    for (const fs::path &path : fs::recursive_directory_iterator(directory)) {
        if (fs::is_regular_file(path)) {
            std::string email = path.filename();
            std::transform(email.begin(), email.end(), email.begin(),
                           ::tolower);
            if (generate_hash(req.algo, email) == req.hash) {
                return email;
            }
            if (email == "default") {
                default_present = true;
            }
        }
    }

    return default_present ? "default" : "";
}

bool is_valid(const std::string_view hash) {
    auto not_hex{[](const char c) {
        if (c >= 0x61 && c <= 0x66) { // a-f
            return false;
        }
        if (c >= 0x30 && c <= 0x39) { // 0-9
            return false;
        }
        return true;
    }};

    return !std::any_of(hash.begin(), hash.end(), not_hex);
}

} // namespace libravatarserv::hash